Changes in the speed that ice travels in more than 200 outlet glaciers indicates that Greenland’s contribution to rising sea level in the 21st century could be significantly less than the upper limits some scientists thought possible.

The finding comes from a paper funded by the National Science Foundation (NSF) and NASA and published in today’s journal Science.

While the study indicates that a melting Greenland’s contributions to rising sea levels could be less than expected, researchers concede that more work needs to be done before any definitive trend can be identified.

Studies like this one are designed to examine more closely and in greater detail what is actually happening with the ice sheets, often using newer and more precise tools and thereby better defining the parameters that scientists use to make predictions, such as the upper limits of sea-level rise.

“This study provides more evidence that the rate at which these glaciers can dump ice into the ocean is indeed limited,” said Ian Howat, assistant professor of Earth sciences and member of the Byrd Polar Research Center at Ohio State University, a co-author on the paper. “What remains to be seen is how long the acceleration will continue–but it appears that our worst-case scenarios aren’t likely.”

The fate of the Earth’s ice sheets and their potential contributions to sea-level rise as the globe warms are among the major scientific uncertainties cited in the Fourth Assessment of the Intergovernmental Panel on Climate Change (IPCC). This is in part because the Greenland and Antarctic ice sheets have historically been, and in large measure continue to be, relatively sparsely monitored, as compared to other parts of the globe.

The faster the glaciers move, the more ice and melt water they release into the ocean.

In previous studies, scientists trying to understand the contribution of melting ice to rising sea level in a warming world considered a scenario in which the Greenland glaciers would either double or increase by as much as ten-fold their velocity between 2000 and 2010 and then stabilize at the higher speed.

This new study shows Greenland ice would likely move at the lower rate–a doubling of its speed–and contribute about four inches to rising sea level by 2100. The previous studies used the higher speed and estimated the glaciers would contribute nearly 19 inches by the end of this century.

In the new study, the scientists extracted a decade-long record of changes in Greenland outlet glaciers by producing velocity maps using data from the Canadian Space Agency’s Radarsat-1 satellite, Germany’s TerraSar-X satellite and Japan’s Advanced Land Observation Satellite. They started with the winter of 2000-01 and then repeated the process for each winter from 2005-06 through 2010-11 and found that the outlet glaciers had not increased in velocity as much as had been speculated.

“So far, on average we’re seeing about a 30 percent speedup in 10 years [of Greenland glaciers, which gives new insight for rising sea level],” said Twila Moon, a University of Washington doctoral student in Earth and space sciences and lead author of the paper documenting the observations.

“This study is a great example of the power of high-resolution data sets in both space and time, and the importance of looking carefully at as much data as possible in helping make the best predictions we can of future changes”, said Henrietta Edmonds, program director for Arctic Natural Sciences in NSF’s Office of Polar Programs.

The scientists saw no clear indication in the new research that the glaciers will stop gaining speed during the rest of the century, and so by 2100 they could reach or exceed the scenario in which they contribute four inches to sea level rise.

The record showed a complex pattern of behavior. Nearly all of Greenland’s largest glaciers that end on land move at top speeds of 30 to 325 feet a year, and their changes in speed are small because they are already moving slowly. Glaciers that terminate in fjord ice shelves move at 1,000 feet to a mile a year, but didn’t gain speed appreciably during the decade.

In the East, Southeast and Northwest areas of Greenland, glaciers that end in the ocean can travel seven miles or more in a year. Their changes in speed varied (some even slowed), but on average the speeds increased by 28 percent in the Northwest and 32 percent in the Southeast during the decade.

Moon said she was drawn to the research from a desire to take the large store of data available from the satellites and put it into a usable form to understand what is happening to Greenland’s ice. “We don’t have a really good handle on it and we need to have that if we’re going to understand the effects of climate change,” she said. “We are going to need to continue to look at all of the ice sheet to see how it’s changing, and we are going to need to continue to work on some tough details to understand how individual glaciers change.”

32 thoughts on “Glaciers can speed up, but can’t put out”

“We don’t have a really good handle on it and we need to have that if we’re going to understand the effects of climate change,” she said. “We are going to need to continue to look at all of the ice sheet to see how it’s changing, and we are going to need to continue to work on some tough details to understand how individual glaciers change.”

Interesting position into which they have put the Climate Science Funding people.
“Give us more money or we will publish an answer that you will really not like.”

I think Andrew30 has got it right: “Give us more money or we will publish an answer that you will really not like.” I hope a few more jump on that bandwagon, we might get a flurry of “Could go the other way” reports and papers that overall might just pull back on the alarmism… Or am I just hoping?

They started with the winter of 2000-01 and then repeated the process for each winter from 2005-06 through 2010-11 and found that the outlet glaciers had not increased in velocity as much as had been speculated
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horse poop……
They started at the highest snow cover….and lowest melt season

if they had started at the beginning of the record…they would have found something completely different

horse poop……
They started at the highest snow cover….and lowest melt season

if they had started at the beginning of the record…they would have found something completely different….
____________________________________
Latitude, you just do not understand how the new post-normal science works. First you figure out what answer will generate the most future grant money and then you do an initial paper that waffles and indicates if future very lucrative grants are not forth coming the results may not please the grant givers.

The scientists saw no clear indication in the new research that the glaciers will stop gaining speed during the rest of the century, and so by 2100 they could reach or exceed the scenario in which they contribute four inches to sea level rise.

What signal did they expect. A polar writing the future in the snow. Classic ” we didn’t really say that they are not accelerating as quickly as we thought because they could exceed the max scenario by 2100.

I think Andrew30 hit upon a brilliant observation. Perhaps the old, tired meme of “more study is needed” will gradually be replaced with “more study is needed – or else.” It is certainly something to ponder. At least in the US the general public is slowly becoming more aware of the vast sums of taxpayer money that is being pounded down the rathole that is “climate science.” Of course the researchers run the risk of not being published if their results run counter to the approved dogma of journals like Science, Nature, PNAS, Scientific American, etc. But the NSF is jealously protective of their “approved” AGW meme so it may prove effective in the long run.

I would love to see one of learned contributors here at WUWT submit an article that describes exactly how government funded (i.e. taxpayer funded) research monies are doled out. On the face of it the process appears to be far more political and agenda driven than a process based on merit.

For instance, it may be fascinating for marine biologists to study the feeding and migratory behavior of the Humbolt squid (with special reference to global warming, of course), but this information is virtually useless to the taxpaying public who just bought a new research vessel and all new equipment for a California university. What do y’all think?

Amazing how when people actually look at glaciers instead of just speculating about them, rivers of ice are a lot like rivers of water. So in the Himalayas, some are getting bigger, some are getting smaller, and some are staying about the same size over a given period. Now we find that in Greenland, some are speeding up, some are slowing down, and others are remaining about the same.

OK, it’s lower than the high end of the IPCC estimate of 19″. What was the low estimate?
Is 4″ lower than the lower end.
Not only “it appears that our worst-case scenarios aren’t likely” as they put it but, maybe it’s not nearly as bad as they were screaming about while arm waving, blowing up people and dropping poley bears from the sky.

This figure showing all the models contribution to SLR for the next 300 years doesn’t give much hope for dangerous SLR at all.http://rsta.royalsocietypublishing.org/content/364/1844/1709/F4.expansion.html
I’ve read that Antarctica holds 89%of the planet’s fresh water and Greenland about 10%, so if Greenland ( all models positive for SLR) is showing some melting until 2300 but Antarctica is still negative ( all models are negative) for SLR until 2300 where does the water come from to give us dangerous SLR?

i believe that this is more of a fluid flow/hydraulics thing. somewhere there is an area that acts as an orifice in the case of each of these galaciers and that governs the movement of the glacier downstream.

in other words the “orifice” controls the volume/speed and the larger the flow channel down stream of the orifice the slower the glacier will move.

of course by murphy’s law this “orifice” will be nearly impossible to examine for size as it will be buried under a mass of moving ice.

Galloping glaciers=mass imbalance. A fast glacier isn’t necessarily a melting one. It’s fast in response to mass added to the ice-field feeding it. It takes a while for snow to turn to ice, and once the critical point is reached, the glaciers speed up. Maybe today’s global sea level stasis is due to mass being added to icecaps (despite the gloomist chant). Just sayin’. Seems to me to be one of the elementary principles taught in a Pleistocene Geology course 30 years ago, back when principles were still taught.

Only a portion of water reaches the base, the majority seque-ing into inter-ice channels. These are the channels that leave eskers after the ice leaves (including those on Mars, of which there are several spectacular ones near the south pole). The ability to speed up the flow of glaciers through basal lubrication is limited and self-limiting: once the limit is reached, the rest goes into internal ice channels. This redistribution into channels actually reduces the amount available for basal lubrication. Internal channels are natural, normal and to be expected in any melting scenario, including those in which melting is only a summer event.

Increased plasticity requires a temperature movement down through the ice mass. It is considered by the IPCC that after about 80 years the summer-winter, day-to-day pulses of air pressure and, therefore, temperature, do not touch the ice. This is the reason that ice measurements of isotopes, CO2 etc. have about an 80 year accuracy. Temperatures at the base of the Greenland and Antarctic glacial masses are somewhere in the -19C, except, of course, where volcanoes exist to raise the temperatures (as at Lake Vostok). Plasticity increases are not significant when you realise that thermal conductivities are such that a) temperatures at the surface take a long time to make their presence felt and 2) even when such temperature changes do reach the bottom, the change in plasticity is minimal. Beyond that, if the ice thickness is <100m or so, the ice is no longer plastic but brittle, and is pushed along from behind.

Increased throughput by reduced terminus back-pressure is considered significant when the ice-shelves break off in Antarctica. In Greenland, however, valley glaciers are the poster-child of global warming. The terminus problem went a long time ago. The glaciers have been moving back up the glacial valleys since the 1880s or earlier. In fact, the claims of the warmists is that the meltwater from glaciers is in danger of stopping, i.e. there is less than before. That says that melting volumes are decreasing, not increasing.

You cannot have an increased sea-level rise due to glacial melt unless more ice melts than before. Ice masses are measured from space, looking down at the surface, They take account of isostatic rebound, but the mass loss is determined by their calculation of the increased distance from satellite to surface, a value beset by many complications that require assumptions, error bars and other, error-constrained values (like ice area). If large mass losses are occurring, yet glacial tongues are not increasing, then the only way temperature increases can be significant is if meltwater outflow increased.

Where, I ask, are the new Mississippis? Where are the increases in meltwater outflow? Where are the glacial meltwater valleys being eroded and expanded, the muddy outflow waters spilling into the oceans and driving away clean-water, saline-loving fish?

There is, however, a different, non-temperature rise way of losing glacial ice mass: sublimation. How much sublimation is lost by a temperature increase from an average of -10 to -8, or summer average from -2 to -1 C (being generous here). Not much. How much is lost from a decrease in cloud cover with its resultant increase in cloudless, sunny sky? A lot.

You only have to hike above the summer snow line to see what happens on a sunny day versus a cloudy day. Even if the terminus doesn't show a meltwater rate change, the snow thickness decreases. Hike up, hike down, look at the snow that was on or near rocks, and it is gone.

I fail to see the huge meltwater increases CAGW claims results from global warming. The numbers I see look like a lot of the mass loss is both mathematical, not necessarily real, and sublimation related. Which is sunshine related.

Show me where the new Mississippi rivers are, and I'll be moving to your side. Tell me that the glacial meltwater streams are decreasing, that valley glaciers are moving upstream and exposing new lands, and I suggest you are more on my, skeptical, side than you realise.

There is, however, a different, non-temperature rise way of losing glacial ice mass: sublimation. How much sublimation is lost by a temperature increase from an average of -10 to -8, or summer average from -2 to -1 C (being generous here). Not much. How much is lost from a decrease in cloud cover with its resultant increase in cloudless, sunny sky? A lot.

I came to the same conclusion, based primarily on the fact that in a number of places south facing glaciers are retreating while north facing glaciers are advancing. Mt Ranier, for example. Volcanoes are nicely symetrical so its easy to see this phenomena.

You can’t get this effect from increasing air temperatures. The cause is highly likely to be increased .insolation and likely some contribution from particulate deposition (albedo change).

Nearly all of Greenland’s largest glaciers that end on land move at top speeds of 30 to 325 feet a year, and their changes in speed are small because they are already moving slowly. Glaciers that terminate in fjord ice shelves move at 1,000 feet to a mile a year, but didn’t gain speed appreciably during the decade.

Growth and acceleration of glaciers that end on land is surely not a “loss” of ice. Only melting and shortening of land glaciers is a “loss”.

Somebody donate these guys another brain cell. The one they’ve got is breaking down from overwork and stress.

Nearly all of Greenland’s largest glaciers that end on land move at top speeds of 30 to 325 feet a year, and their changes in speed are small because they are already moving slowly. Glaciers that terminate in fjord ice shelves move at 1,000 feet to a mile a year, but didn’t gain speed appreciably during the decade.

The speed difference is due to ice floating on water offering minimal resistance to the ice pushing from behind.

Which indicates the reason the land terminating glaciers are accelerating is due to mass loss toward their terminus. And why mass loss on ocean terminating glaciers doesn’t cause acceleration.

But it doesn’t tell us why glaciers are losing mass toward their terminus.

Philip Bradley says:
May 8, 2012 at 6:53 pm
… in a number of places south facing glaciers are retreating while north facing glaciers are advancing. Mt Ranier, for example. Volcanoes are nicely symetrical so its easy to see this phenomena.

This is brilliant! and the reason internet discussions are so valuable. A testable idea of sublimation based on insolation (and relative humidity?), using disproportionally shadowed glaciers (ice caps?) showing mass loss.

My overall question about warming acceleration of ice loss is that glacial calving loss, the way that valley glaciers that reach the sea, shows up as increased iceberg volume, which is not reported. Valley glacier loss is reported as “movement” up valley of the glacier terminus, especially if it has moved onto ground, exposing fresh surfaces. The only way an increase in loss from global warming can then be seen is through increased outflow. If anything, the warnings are of icemelt volumes going down. So melt rates cannot be going up.

Sublimation loss occurs through either increased insolation or through reduced relative humidity, or a combination of both. Decreased cloudiness is not allowed under CAGW, and an INCREASE in relative humidity is required under CAGW (to make more rain or snow). So the sublimation loss is not acceptable under CAGW. CAGW now has a bind. All glacial mass loss increases must result in more icebergs and more meltwater reaching the oceans. Which we don’t see.

The volumes to achieve larger sea-level rises are enormous. The number of significant drainage points on Greenland and the Antarctic are few. Both Greenland and the Antarctic have only 4 or 5 months in which melting can occur. All the meltwater must be concentrated in just a few spots during a few months, focused on perhaps two months out of the 4 or 5. The volume that must come out during that peak time would be noticeable if it were of the amount the CAGW say is going on.

“How does a glacier “end on land”? I would think that the ice eventually reaches the ocean. Maybe they mean glaciers that terminate at another glacier.”

I have walked up the Roseg Valley in the Uberengadine in Switzerland, passing all the little pegs put in one every 10 years to mark the position of the snout of the glacier at that time. These go back more than a century. The Glacier used to end in the great Bernina glacier which is long gone. A melting glacier is a ‘retreating’ glacier, so-called for good reason. I learned, at school, that gravity acts on the mass of the ice and only a growing, heavier glacier speeds up (advances). I am quite unable to visualise the end result of a melting glacier speeding up – would the entire glacier come flowing down the valley and into the sea (or whatever)? Has anything like that ever happened? What would that look like?

Could water really ‘lubricate’ the underside of a glacier to speed it up? The glacier not only grinds grooves on solid rock due to its weight but drags along huge boulders weighing many tons (erratics)

If the glacier is advancing due to getting heavier it cannot increase sea-level.

What I learned at school and subsequently seems to make sense and is logical. I’ll need a lot of convincing that this all wrong.

For a glacier to move faster, it needs more ice gain at the top. If it’s losing ice, it thins and slows down. Melting isn’t all that relevant for those ending in the sea (they break off and float away). For those in mountains, it is the elevation change to a warmer lower point that matters.

For E.M.Smith, You are going contra to National Geographic, I think. In the September 2004 Global Warming edition, they note that 1. The buckskin Glacier in Denali national Park is losing 23 cubic miles of water a year and is the largest glacial contribution to sea-level rise on Earth. Is this a feasible claim? . This is box-captioned “It’s not a belief system; it’s an observable scientic fact”.
If you disobey Nat Geo, you might be like Peter Sellers in Dr Strangelove when, to get some coins to phone the President, he asks the marine with the gun if he can break into a Coca Cola machine. The answer was along the lines, “If this turns out a fake, you’ll have to answer to the President of the Coca Cola Corporation” an undoubted authority figure.